How does negative feedback differ from positive feedback?

Answer 1

A general overview:

Negative feedback means that a product/end result will dictate reducing further output whereas positive feedback means that the product/end result will dictate increasing output.

Answer 2

Negative feedback results in the stimulus being reversed. Example: when your body temperature is too cold, your muscles shiver to generate heat. When enough heat is generated that your body temperature is back within homeostatic range, you stop shivering because heat is no longer necessary. Similarly, when you body temperature is too high, you will begin to sweat. When sweat evaporates form your skin, it takes heat with it, thus cooling your body. When your temperature is back within homeostatic range, you stop sweating because you no longer need to cool down. Additional examples: when you experience an itch, you scratch it until it does not itch anymore, you experience the sensation of hunger until you eat a certain amount and experience satiation (not feeling hungry) until you have used a certain amount of stored energy. The vast majority of biological processes occurring in our bodies utilize negative feedback to maintain homeostasis.

Positive feedback results in the stimulus persisting. Example: When a baby in utero grows to exert enough force on the cervix, stretch receptors are activated and relay back to the brain. The brain releases oxytocin to initiate uterine contractions to push on the baby. This adds more force onto the cervix, stimulates the stretch receptors more, more oxytocin is released, and more uterine contractions push on the baby to push on the cervix to stimulate the stretch receptors to cause more oxytocin release and trigger more uterine contractions and so on... This cycle is stopped when the baby exits the womb because there is no longer a force being exerted on the cervix, so the stretch receptors are not activated to relay signals to the brain, and the brain will not release oxytocin to trigger uterine contractions anymore.